Process of treating fresh fruits and vegetables and compositions for use therein

ABSTRACT

A method of inhibiting undesirable changes in color, plasmolysis and decay of fresh fruit and vegetables (whole, sliced or shredded) by contacting the same with a liquid treating agent containing benzyl alcohol. The method employs two successive reactions, the first involving naturally occurring oxidases and the second the formation of benzoic acid. Use of solubilizing agents to facilitate the formation of aqueous solutions of benzyl alcohol, and examples of effective ranges of concentration are given.

United States Patent Sharma 51 Mar. 28, 1972 [54] PROCESS OF TREATINGFRESH FRUITS AND VEGETABLES AND COMPOSITIONS FOR USE THEREIN [72]Inventor: Jagan N. Sharma, West Los Angeles,

Calif.

[73] Assignee: Zenith Processing Corporation, Venice,

Calif.

22 Filed: Jan. 28, 1970 [21] App]. No.: 6,546

[52] US. Cl. ..99/l54, 99/100 R, 99/103 [51] Int. Cl ..A23b 7/14, A2313/34 [58] Field of Search ..99/l00, 103, 154, 156, 222,

99/224, 193, DIG. 1; 252/407 [56] References Cited UNITED STATES PATENTSFrandsen ..99/1 56 2,622,032 12/1952 Frandsen 2,698,804 1/1955 PrimaryExaminer-Norman Yudkofi' Assistant Examiner-Martin G. MullenAttarneyMiketta, Glenny, Poms and Smith [57] I ABSTRACT A method ofinhibiting undesirable changes in color, plasmolysis and decay of freshfruit and vegetables (whole, sliced or v 8 Claims, No Drawings PROCESSOF TREATING FRESH FRUITS AND VEGETABLES AND COMPOSITIONS FOR USE THEREINBACKGROUND OF THE INVENTION Plasmolysis and discoloration of freshvegetables and cut fruit and vegetables has plagued the fruit andvegetable industry for many years. The term plasmolysis" as used hereinrefers to the softening, sliming and degenerated appearance and feel ofplant cells, particularly leaves and the cut stems of many vegetables,which takes place quite rapidly and greatly detracts from the salabilityof vegetables when they arrive at the retail market. The discolorationand sliminess is very often observed on the cut stems of various leafyvegetables such as lettcce, chicory, endive and the like, in the form ofa reddish discoloration which spreads to the stems of the leaves.Broccoli, cauliflower and other vegetables are prone to develop theyellowish or brownish discoloration not only on the stems, but also onthe heads of these vegetables. Sliced bananas, apples and potatoesdevelop discoloration which persists when such slices are subsequentlydehydrated or cooked and impairs the salability of such products.

Prior US. Pat. No. 2,215,446 was concerned with this problem as itaffects leafy vegetables such as lettuce and attempted to prevent suchdiscoloration by placing the butts or cut stems of the lettuce incontact with a porous fibrous carrier saturated with a solution ofsodium thiosulfate. US. Pat. No. 2,453,040 utilized solutions offormaldehyde in the same manner. During recent years however, greatchanges have taken place in the manner in which these leafy vegetablesare picked, packed and shipped and the prior materials and methods arenot applicable. Lettuce for example, is not being shipped in crates orboxes, packed with crushed ice between layers of such lettuce. Instead,the customary method of harvesting lettuce and similar leafy vegetablesis to have the workers cut the plant from its root stalk and leave theplant in rows on the field. Empty boxes are laid along the rows and asubsequent group of workers, each provided with a portable canister ofwater and a hand spray, arranges a layer of lettuce heads in a box andsprays them with water by hand, this process being repeated for thesecond or sometimes third layer of lettuce in a box. These boxes orcartons are subsequently taken to a so-called packing house which isgenerally reached in 3 to 6 hours from the time that the heads have beencut, this period of time being sufficient to initiate the development ofthe discoloration which takes place at the exposed cells of the stem.The boxes are then placed into a large vacuum chamber at the packinghouse and subjected to the action of vacuum which withdraws moisturerapidly and thereby reduces the temperature of the cut lettuce in theboxes to about 34 F. The now chilled lettuce in its boxes is placed intorailroad cars or trucks and ice is placed in the bunkers of thesevehicles or cars so as to maintain the atmosphere fairly low. However,no ice is placed on top of the boxes or is in contact with the lettuce.The prior methods are therefore incapable of being employed.

The present invention utilizes reactions with oxidases which are presentin plant and fruit cells and juices, whereby the unique properties ofthe compounds and chemicals disclosed herein rapidly cause the formationof reaction products in situ on the surfaces of the vegetables and fruitand prevent or greatly retard the discoloration, plasmolysis anddegenerative changes which impair ultimate salability of vegetables,fruit and products made therefrom. The mode of operation is particularlyadapted for use during harvesting and handling procedures describedabove and now employed with leafy vegetables such as the variousvarieties of lettuce, endive and chicory, and for use in the treatmentof peeled and sliced fruit and vegetables such as bananas, apples andpotatoes which are eventually sold as chips or dehydrated or partlycooked or fried products. Moreover, one of the unique aspects of thepresent invention lies in the successive production of two reactions bythe use of but a single chemical, the first reaction rendering theoxidases innocuous and the second producting a preservative whichretards plasmolysis and decay.

An object of the present invention therefore is to provide a method oftreating fresh fruits and vegetables in a simple manner whereby theoxidases which cause darkening and discoloration are rendered innocuousand plasmolysis and decay is greatly retarded or inhibited.

Another object is to disclose and provide a method whereby twosuccessive reactions are caused to take place on the surface of freshfruit and vegetables, the first reaction inhibiting darkening ordiscoloration and a subsequent reaction forming a minute deposit of areaction product which enhances the keeping properties of the fruits andvegetables.

Another object is to disclose the employment of the unique properties ofbenzyl alcohol and liquid compositions containing benzyl alcohol, in thetreatment of fresh fruits and vegetables to inhibit discoloration andretard plasmolysis and decay during shipment and storage of such fruitsand vegetables.

Another object of the invention is to disclose treating compositionscontaining preferred contents of benzyl alcohol, adapted for use in themethod of this invention.

Again, an object of the invention is to disclose and provide benzylalcohol containing an agent adapted to facilitate the formation ofaqueous compositions which contain desired concentrations of benzylalcohol and which are stable and not subject to rapid stratification.

The methods, reactions, chemicals employed, and advantages and uses ofthe present invention will be apparent to those skilled in the art fromthe following more detailed description in which reference will be madeto specific examples.

The aqueous, liquid treating composition which is brought into contactwith the fresh fruit and vegetables and particularly with the cut orbroken areas of the plant, fruit or vegetable in accordance with thisinvention, contains benzyl alcohol. Although agitation or homogenizationexpedites the dispersion and solution of benzyl alcohol in water so asto produce liquid compositions containing from between 0.4 percent and 4percent by weight of benzyl alcohol, adapted for use in the method ofthis invention, it is often desirable to add an agent adapted to enhancethe miscibility of the benzyl alcohol with water. Moreover, it is oftendesirable to make a base composition containing a high content of benzylalcohol for shipment to various parts of the country, the basecomposition then being added to large amounts of water to producetreating compounds containing benzyl alcohol within the range stated.Various agents adapted to enhance the miscibility and solubility ofbenzyl alcohol in water and to improve the stability (absence ofstratification upon standing) of the composition and reduce mixing time,may be employed. The addition of small quantities of sodium dioctylsulfosuccinate (generally between about 4 percent and 10 percent byweight of benzyl alcohol) has been found very effective. A concentratedbase composition may therefore contain from 50 percent to 96 percent byweight of benzyl alcohol with from 4 percent to 10 percent of the agentand from 0 percent to 46 percent of water. These solutions containinghigh content of benzyl alcohol may be added to predetermined amounts ofwater in the field, with agitation, and it will be found that the benzylalcohol and blending agent will be readily miscible with the waterforming what appears to be a clear solution which is stable. It is to beunderstood that the presence of other chemicals in the treatingcomposition is not precluded.

When field crops of fresh leafy vegetables such as lettuce are beingharvested in the manner previously described, the stem is cut and thecell structure exposed. The presence of naturally occurring oxidases inthe cells and its juices is believed to be the cause of the undesirablediscoloration which forms rapidly and which becomes pronounced within afew hours. Shortly after the plants have been severed from the soil,other workers place them in cartons, crates or boxes and, in accordancewith this invention, contact the plants and particularly the cut orsevered stems with the aqueous liquid composition preferably containingfrom about 2 percent to about 4 percent of benzyl alcohol. Usually suchcontact can be effectively obtained by spraying the plants while in thefield box or being destroyed, absorbed and rendered innocuous by thereaction. Colorless benzyl aldehyde is believed to be the reactionproduct which diffuses somewhat into the cells adjacent the surface ofthe plants (or other fruit and vegetables being treated). The reactiontakes place within about 1% to 2 hours: in the case of lettuce, aninterval of between 3 to 6 hours normally occurs between the sprayapplication of the treating composition and the introduction of thelettuce into the vacuum chamber in which the crated lettuce is chilledby the vaporization of water, thus providing adequate reaction time.

After the oxidases have been rendered innocuous as stated hereinabove,the first reaction product left on the treated vegetable is-rapidlyconverted by exposure to air into a minute discontinuous deposit ofbenzoic acid on all surfaces of the treated fruit or vegetable, toproduce another valuable function, namely preservation and immunizationfrom plasmolysis and decay. This last formation of benzoic acid in situmay take place, in part at least, before lettuce is chilled by theremoval of water (as previously described) or after chilling and duringsubsequent shipment. The formation of benzoic acid and its preservativefunction are obtained even when the chilling step is omitted and as soonas excess moisture evaporates.

The reactions which take place may be said to involve It may be notedthat the solubility of the reaction product (benzyl aldehyde) is low andalmost all of it is formed and remains on the surface of the treatedfresh fruit, vegetable or green. The benzoic acid has a very lowsolubility in water and is also left on the surface. In actual practice,only about one pint of the liquid aqueous composition containing say 2percent by weight of benzyl alcohol is used in spray treating a crate oflettuce containing about 36 heads, and even if the entire pint were toremain on the lettuce and be entirely converted to benzoic acid, thetreated lettuce would carry less than 0.05 percent by weight of benzoicacid. Actually however, a proportion of such pint applied as a forcefulspray is used in flushing off soil adhering to the heads and does notremain on the lettuce.

The method herein disclosed can be effectively used on broccoli,cauliflower and other vegetables which tend to turn yellow or brown, notonly at the stem ends but at the leaves and flowerlets. Similarly,freshly peeled and sliced fruit and vegetables such as potatoes, applesand bananas may be treated in order to inhibit darkening ordiscoloration and prevent or retard decay. Oxidases are widelydistributed anzymes which occur in nature and cause darkening. Freshlysliced fruits and vegetables are often dried or partially dehydratedbefore shipment. These food chips are used in compotes and pics, areoften fried or converted into flour. The

present treatment is preferably applied as; soon as the fruit orvegetable has been peeled and sliced: the liquid aqueous mediumcontaining benzyl alcohol in the lower portion of the range (say fromabout 0.4 percent to about 2 percent by weight) may be sprayed on suchslices or the slices may quickly pass through a bath of the treatingcomposition and excess liquid removed by the use of vibrating screens ora blast of air.

Substantially the same procedure may be used for treating and prolongingthe effectively utilizable life of sliced or shredded salad greens (suchas lettuce, romaine, celery,

cabbage, carrots, etc.) often sold in plastic bags to institutions andretail markets. Discoloration and plasmolysis is inhibited for as longas 10 days to 2 weeks by dipping or otherwise contacting the shreddedvegetables and greens to a bath containing the benzyl alcohol and thenremoving the excess treating solution by vibrating or rotating screensor centrifuge, before packing in bags or containers.

Those engaged in the production, packing, shipment and sale of freshfruits and vegetables and dried fruits and vegetables will readilyappreciate the advantageous results and benefits obtained by the presentinvention. It is economical and adapted to normal handling procedures.It permits fresh vegetables to be delivered in prime condition todistant markets, and command premium prices. A retailer need not cut offdiscolored stems and strip ofi outer leaves in an attempt to sell hisproduce. Dehydrated sliced fruit or sliced and frozen potatoes are lightin color and withstand storage without degeneration'or decay whentreated in accordance with the disclosures made herein.

I claim:

1. In a method of rendering inactive naturally present oxidases in cellsadjacent the surface of fresh fruits and vegetables and inhibitingundesirable color changes and plasmolysis of such fruits and vegetables,the step of spraying fresh fruit and vegetable with an aqueous mediumcontaining from about 0.4 percent to about 4.0 percent of benzylalcohol.

2. A method as stated in claim 1 whereby said benzyl alcohol reacts withsaid oxidases to form benzaldehyde and discoloration of fruit andvegetables is inhibited, and then exposing the fruit so treated to theaction of air to form benzoic acid in situ on the surface of the fruitand vegetable to enhance the keeping qualities of the fruit andvegetables.

3. A method as stated in claim 1 wherein the vegetables treated areleafy vegetables, including lettuce, endive and chicory and the aqueousmedium contains between about 2 percent and 4 percent of benzyl alcohol.

4. A method as stated in claim 1 wherein the fruit and vegetablestreated are peeled and sliced and the aqueous medium contains betweenabout 0.4 percent and 2 percent of benzyl alcohol.

5. In a method of inhibiting surface discoloration of cut and injuredfruit and vegetables and also enhancing the keeping qualities thereof,the step of contacting the cut and injured surfaces of fresh fruit andvegetables with an aqueous medium containing from between about 0.4percent and 4 percent of benzyl alcohol.

6. A method as stated in claim 5 wherein the aqueous medium ismaintained in contact with said cuts and injuriesv for a time suificientto permit reaction between the benzyl alcohol and oxidases in said cutsand injuries.

7. A method as stated in claim 6 wherein the fruits and vegetables aresubsequently exposed to the action of air to form benzoic acid in situand said cuts and vegetables.

8. A fresh plant, vegetable or fruit exhibiting at least one cut surfaceexposing its cell structure, such cell structure of said surfacecarrying a benzoic acid residue of a reaction between benzyl alcohol,naturally occurring oxidases and air.

2. A method as stated in claim 1 whereby said benzyl alcohol reacts withsaid oxidases to form benzaldehyde and discoloration of fruit andvegetables is inhibited, and then exposing the fruit so treated to theaction of air to form benzoic acid in situ on the surface of the fruitand vegetable to enhance the keeping qualities of the fruit andvegetables.
 3. A method as stated in claim 1 wherein the vegetablestreated are leafy vegetables, including lettuce, endive and chicory andthe aqueous medium contains between about 2 percent and 4 percent ofbenzyl alcohol.
 4. A Method as stated in claim 1 wherein the fruit andvegetables treated are peeled and sliced and the aqueous medium containsbetween about 0.4 percent and 2 percent of benzyl alcohol.
 5. In amethod of inhibiting surface discoloration of cut and injured fruit andvegetables and also enhancing the keeping qualities thereof, the step ofcontacting the cut and injured surfaces of fresh fruit and vegetableswith an aqueous medium containing from between about 0.4 percent and 4percent of benzyl alcohol.
 6. A method as stated in claim 5 wherein theaqueous medium is maintained in contact with said cuts and injuries fora time sufficient to permit reaction between the benzyl alcohol andoxidases in said cuts and injuries.
 7. A method as stated in claim 6wherein the fruits and vegetables are subsequently exposed to the actionof air to form benzoic acid in situ and said cuts and vegetables.
 8. Afresh plant, vegetable or fruit exhibiting at least one cut surfaceexposing its cell structure, such cell structure of said surfacecarrying a benzoic acid residue of a reaction between benzyl alcohol,naturally occurring oxidases and air.